INTRODUCTORY. 5 



is separate. Its hinder ends work in cavities on the lower part 

 of the skull, and are held in position by strong ligaments and 

 muscles. 



The ribs are attached to the dorsal vertebras, and connect by 

 cartilage at the other end with the sternum or breastbone 

 really a series of united bones in the middle line of the chest 

 (thorax). The blade-bones (scapula) of the fore-limbs are 

 attached to the upper ribs by the flat or concave side ; and the 

 hinder limbs are connected strongly to the sacrum by means of 

 the hip-bones which are united below to form the pelvis, to 



Skeleton of the Common Badger. 



which the thigh-bone is jointed. The Reptiles and Amphibians 

 exhibit some differences in their skeletal structure which will be 

 pointed out later. 



In the matter of teeth there is great diversity among the 

 Mammals even in the small number of British species. With 

 a view to a proper understanding of the teeth in, say, the 

 Rodents and the Ungulates, it is necessary to write a few words 

 respecting tooth-structure. Although in adult Mammals the 

 teeth are so intimately connected with the jaw as to appear 

 outgrowths from it, this is not the case really. They originate 

 in the skin which covers the jaw, and the most effective part of 

 their structure the enamel is derived from the epidermis, the 



